In large format printing, e.g. poster printing, billboard printing, wherein the weatherability of the print is very important, silk-screen printing is still a dominant printing method. This method has however drawbacks. The method is rather time consuming since for every colour a dedicated screen has to be made and printed and the method is basically analog.
More and more images to be printed are available in digital form, so that also in the printing of large formats, digital addressable printing techniques become indispensable.
A well known digital addressable printing technique that is useful for large format printing is ink-jet printing, both with water based inks and with solvent based inks. An example of an ink-jet printer for large format printing can be found in, e.g., U.S. Pat. No. 5,488,397, wherein a printer is disclosed having two or more parallel ink-cartridges shuttling over the width of the substrate to be printed while the substrate moves in a direction basically perpendicular to the direction of movement of the shuttling ink-cartridges.
In WO 96/01489 an ink-jet printer for large format printing is disclosed wherein a single ink-cartridge shuttles over the substrate to be printed.
In U.S. Pat. No. 4,864,328 an ink-jet printer is disclosed, wherein only one printing engine (ink-jet head)having a multiple array of nozzles is moved as a shuttle over the paper.
In EP-A-526 205 again an ink-jet printer is disclosed, wherein only one printing engine (ink-jet head)having a multiple array of nozzles is moved as a shuttle over the paper.
A commercial ink-jet printer INDANIT 162Ad (trade name) available from Indanit Technologies, Israel, uses multiple ink-jet printheads mounted in a staggered position over the width of the substrate to be printed. In this device the printing substrate has to pass several times under the array of staggered ink-jet printheads while between each pass the printheads are slightly moved in a direction parallel to the width of the substrate. This multi-pass printing enhances the resolution that can be printed, while in the printhead itself the nozzle can be positioned fairly far apart.
Although ink-jet printing provides the possibility for printing large formats in a short time, the possible printing resolution is not always up to the demands, the stability of the image in, e.g., billboards where the image has to be weatherproof leaves still room for improvement.
In U.S. Pat. No. 5,138,336 a thermal printer using at least two thermal printing heads is described for printing on large substrates.
In U.S. Pat. No. 5,237,347 an electrophotographic printer is disclosed wherein a single photoconductor is exposed to the light of several exposure units, so a large latent image can be written on the photoconductor and after development be transferred to a final substrate.
In WO-A-96 18506 a shuttling printer using more than one direct electrostatic printing engine is disclosed wherein these engines are placed one after an other for printing multi-colour swaths.
In the art of printing of large formats, it is however still desired to have still faster printers that use very weatherable marking material, especially toner particles. In toner particles the pigments are imbedded in a resin and thus are the pigments in the image quite protected from the influences of the environment.